Multi-ratio reversing power shiftable gear

ABSTRACT

A multi ratio reversing powershiftable transmission having an input shaft, an output shaft, a plurality of countershafts, a drive wheel set, a distribution wheel set and a driven wheel set. The set of drive wheels includes a driven idler gear on each countershaft which can be optionally non-rotatably connected with the contershaft to cause a change of gear and direction of the transmission. The set of distribution wheels consist of at least one fixed gear on each countershaft for commutating rotation between communicating countershafts and the fixed gears of the set of driven wheels which in turn drive the output shaft.

BACKGROUND OF THE INVENTION

In the building machines used at present, gears are used which canessentially be divided into two groups. Characteristic of one group isthat on the powershift gear is a front mounted hydrostatic driving unit.In this gear, the speed and torque of the splitter group are adapted byhydraulic or electrohydraulic controls.

The predominant number of gears used belongs to the other group of thepowershiftable gear with front-mounted, hydrodynamic torque converters.By means of said driving unit, it is possible to obtain a continuous andautomatic torque multiplication with increasing working resistance ofthe motor vehicle such as a building machine. Here gear input torquescan be produced which substantially correspond to the triple value ofthe engine torque. This is significant, since differently from what isthe case in the passenger car, the work is done with the gear orconverter. In a loader, for example, the shovel is pushed into absorbingground. The filling is broken up and lifted. For loading the vehicle isreversed, the shovel is further lifted and unloaded. The torqueconversion is a great advantage precisely at low speeds and great speeddifferences between the input and output.

The converter can be complemented by a converter bridge clutch. By meansof said clutch it is possible to obtain a considerable reduction ofconsumption within the gears in the range of higher speeds.

The power flow in the individual gears is produced by a combination ofhydraulically shiftable clutches. Among other things, said clutches mustbe powershiftable for reversing and, therefore, absorb much energy. Thedesign of the housing or arrangement of the shafts of the gear must beadapted to a specific use. Typical cases of use for a reversing gear aredump carts, loaders, excavator loaders and lift trucks, but also invehicles that must be operated on the street such as motor cranes.Depending on the type of vehicle, a specific center distance between theinput and output shafts of the gear is required. Long center distancesare to be maintained, for example, when the angle of inflection ofuniversal shafts must be kept small. In this case, the reversing gearassumes an additional function as a transfer gear.

In lift trucks, the reversing gear has only one output shaft. Due to thespatial conditions a lesser center distance is needed.

In most cases, at least one power take off driven in dependence on theengine speed, for example, for the hydraulic system of the mobilemachine is required. Together with the power take off, a lubricant andshift pump is also provided which likewise is driven depending on theengine speed.

Depending on the type of construction of the vehicle, the tasks to beperformed by a reversing gear are very varied.

DESCRIPTION OF THE RELATED ART

DE-A 11 29 838 has disclosed a reversing gear which stands out by asmall axial length. A fixed pinion is upon an input shaft which isconstantly meshed with fixed pinions upon a reversing shaft and acountershaft. All loose pinions are upon one side of the gear andpermanently meshed with each other. A respective friction clutch issituated between the loose and fixed pinions. In this known reversinggear, the practical construction of the friction clutches, particularlythe arrangement of the sets of plates, the mounting of the loose pinionsupon the countershafts and also the indirect support of the countershaftitself on the side of the loose pinions turns out to be relativelyexpensive.

DE-A 25 35 700 has disclosed a reversing gear in which the frictionclutches are designed as double clutches. In this gear, it is possibleto obtain a relatively high number of gears, but a large installationspace is needed in an axial direction, since up to four gears and onedouble clutch are to be lodged on one countershaft.

SUMMARY OF THE INVENTION

The problem on which this invention is based is to provide a reversingpowershiftable gear with a small axial length which allows differentvariants with fundamentally the same design as to the possible number ofgears and the required center distances.

One possible solution of the stated problem consists in that a singleclutch is situated upon each countershaft, that one fixed gear and idlergears in constant mesh therewith form a set of drive wheels, that onefixed gear situated upon the countershaft with two idler gears are inconstant mesh and form a chain of driven wheels, and that thecountershafts are interconnected by a fixed gear and one idler gearwhich form a set of distribution wheels. Since only one clutch isprovided for each countershaft, an axially short design results even inthe case of a six-ratio reversing gear. Because of their small length,the countershafts have little flexure. They can be supported in the gearhousing on both sides on roller bearings. The used idler gears have asingle meshing; they are not used as intermediate gears. By virtue ofthe proposed design of the countershafts it is likewise possible toobtain long and short center distances.

It has proved advantageous if the fixed gear of the chain of drivenwheels, situated upon the countershaft, is opposite to an idler gear ofthe set of distribution wheels. The fixed gear upon the countershaft,which can also be the output shaft of the gear, has a relatively largediameter. It is preferably helically cut. A large bearing base isavailable for support. Based on the load and speed conditions, it isadvantageous if the clutch for the third gear is coordinated with theidler gear of the set of distribution wheels.

To connect the pinions of the set of distribution wheels, taking intoaccount the requirement of small axial length of the gear, it has provedvery advantageous if a clutch, used as a directional and/or a gearshiftclutch with one idler gear of the set of drive wheels and two fixedgears of the set of distribution wheels, is situated upon thecountershaft. Disregarding the converter housing, the axial length ofthe gear is thus determined by the single clutch and one idler and twofixed gears.

In another solution of the problem on which the invention is based, thechain of driven wheels is formed by idler gears. For this purpose, asingle clutch is situated upon each countershaft, one fixed gear andidler gears in constant mesh therewith form a set of drive wheels, theidler gear situated upon the countershaft is in constant mesh with twoidler gears and the countershafts are interconnected by fixed gearswhich form a set of distribution wheels. Due to the use of one idlergear, the expert is to a great extent free with the spatial arrangementof the countershafts of the gear.

A convenient embodiment of the reversing gear has the input shaftssituated concentrically to each other. One input shaft designed, as ahollow shaft, carries the fixed gear of the set of drive wheels.

Based on the load, speed and spatial conditions, it has proved veryadvantageous that with the idler gears, which are in constant mesh withthe fixed gear, clutches for changing the first and second gear becoordinated.

Other features, essential to the invention and the advantages resultingtherefrom, are to be understood from the description that follows ofseveral embodiments of a powershiftable reversing gear.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a gear diagram of a reversing gear having six forward andthree reverse gears and a long center distance;

FIG. 2 is a diagrammatic front elevation of the reversing gear of FIG. 1to illustrate the spatial position of the countershafts and of the fixedand idler gears;

FIG. 3 is a gear diagram of a reversing gear having six forward andthree reverse gears and a short center distance;

FIG. 4 is a diagrammatic front elevation of the reverse gear of FIG. 3;

FIG. 5 is a gear diagram of another embodiment of a four-gear reversegear with a long center distance; and

FIG. 6 is a diagrammatic front elevation of the reverse gear of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A gear diagram of a powershiftable reversing gear 1 is reproduced inFIG. 1. This is a reversing gear with a maximum of six forward and threereversing gears. A diagrammatically indicated engine 2 drives an inputshaft 3 of the reversing gear. The input shaft 3 is non-rotatablyconnected with an impeller 4 of a hydrodynamic torque converter 5. Aturbine wheel 6 of the hydrodynamic torque converter transfers the inputto a hollow shaft 7 which is concentric with the input shaft 3.

The hydrodynamic torque converter 5 is completed by one stator 8 whichis supported on a free wheel. The operation range of the hydrodynamictorque converter is limited by a converter bridge clutch 9. In aconventional manner, the converter bridge clutch 9 is closed on thethrough drive point so that the impeller 4 is mechanically connectedwith the turbine wheel 6.

The pump 10, appearing to the right in the drawing, is a lubricant pumpsuch as a gear pump driven by the input shaft 3.

A fixed gear 11, which forms the input gear of a set of drive wheels 12,is non-rotatably fitted upon the hollow shaft 7. Idler gears 13, 14 and15 belong to said set of drive wheels 12. The fixed gear 11 is inconstant mesh with said idler gears 13, 14 and 15. The idler gears 13,14 and 15 are each supported on a countershaft 16, 17 and 18.

A clutch 19 is coordinated with the idler gear 13, a clutch 20 with theidler gear 14, and a clutch 21 with the idler gear 15.

When the clutch 19 is engaged, the idler gear 13 is non-rotatablyconnected with the countershaft 16. The idler gear 14 is connected withthe countershaft 17 when the clutch 20 is actuated. If the clutch 21 isengaged, a non-rotatable connection exists between the idler gear 15 andthe countershaft 18. The clutches 19, 20 and 21 allow a reversal of thedirection of rotation of an output shaft 22 of the reversing gear 1. Forthis reason, the clutches 19, 20 and 21 are also designated asdirectional clutches.

Together with the countershafts 16, 17 and 18, the same as the outputshaft 22, the reversing gear has added countershafts 23, 24 and 25.

A fixed gear 26 is situated, together with the idler gear 13, upon thecountershaft 16. The fixed gear 26 is in constant mesh with a fixed gear27 of the countershaft 24. The fixed gear 27 can assume the function ofan intermediate gear. An idler gear 28, which is meshed with the fixedgear 27 of the countershaft 24, is supported upon the countershaft 25.One clutch 29 is coordinated with the idler gear 28 by which the idlergear 28 can be non-rotatably connected with the countershaft 25.

An idler gear 30 is rotatably mounted on the countershaft 24. The idlergear 30 can be non-rotatably attached to the fixed gear 27 by means ofanother clutch 31.

When the clutch 31 is engaged, the input flows via the idler gear 30 toa fixed gear 32 of the countershaft 25.

A fixed gear 33, which is in constant driving connection with the fixedgear 32 of the countershaft 25, is situated upon the output shaft 22 ofthe reversing gear.

The idler gear 30 and the fixed gears 32 and 33 form a chain of drivenwheels 34.

The fixed gears 26, 27 and the hollow gear 28 belong to a set ofdistribution wheels 35 which is completed by another fixed gear 36 ofthe countershaft 17, two fixed gears 37 and 38 of the countershaft 18and one fixed gear 30 of the countershaft 23.

An idler gear 40, which can be non-rotatably connected by a clutch 41with the countershaft 23, is on the countershaft 23. The idler gear 40is in constant mesh, which is indicated by a dotted line 42, with thefixed gear 32. The idler gear 40 thus belongs to the chain of drivenwheels 34.

The fixed gear 27 is meshed, which is made clear by the dotted line 43,with the fixed gear 37 of the set of distribution wheels 35. The idlergear 15 of the countershaft 18 meshes with the fixed gear 11, which isapparent from the dotted line 44.

The clutches 41, 31 and 29, together with the directional clutchesmentioned, serve for gear change and are designated as gear clutches.For each gear one directional and one gear clutch are engaged.

From the hitherto described construction of the reversing gear 1, itresults that the countershafts 16 and 17, each have one idler gear 13and 14 of the set of drive wheels 12 and one fixed gear 26 and 36 of theset of distribution wheels 35.

The clutch 21 is both a directional and a gearshift clutch. The fixedgears 37 and 38 of the set of distribution wheels, together with theidler gear 15 of the set of driving wheels 12, are supported upon thecountershaft. The speed and the direction of rotation of all pinions ofthe set of distribution wheels 35 are defined when one of thedirectional clutches 19, 20 and 21 is actuated.

The countershafts 23, 24 and 25 upon which the clutches 41, 31 and 29(gear clutches), respectively, are situated accommodate one fixed gear39, 27 and one idler gear 28 of the set of distribution wheels 35, thesame as one idler gear 40, 30 and one fixed gear 32 of the chain ofdriven wheels 34. If the reversing gear 1 is operated in a four-gearversion, the following ratios apply:

    ______________________________________                                               gear engaged clutches                                                  ______________________________________                                               1    19 and 41                                                                2    19 and 31                                                                3    19 and 29                                                                4    21 and 29                                                                1R   20 and 41                                                                2R   20 and 31                                                                3R   20 and 29                                                         ______________________________________                                    

For a six-gear version where the clutches 19 and 21 are used asso-called split clutches, the following ratios apply:

    ______________________________________                                               gear engaged clutches                                                  ______________________________________                                               1    19 and 41                                                                2    21 and 41                                                                3    19 and 31                                                                4    21 and 31                                                                5    19 and 29                                                                6    21 and 20                                                                1R   20 and 41                                                                2R   20 and 31                                                                3R   20 and 29                                                         ______________________________________                                    

FIG. 2 is to be understood as a schematized front elevation of thereversing gear 1 according to FIG. 1. The reversing gear works with along center distance. The countershafts 16, 24, 25, 17, 18 and 23 of theset of distribution wheels 35 are interconnected by the thick line(distribution chain). Said distribution chain is broken between theclutch 41, for the first gear (countershaft 23), and the clutch 29 forthe third gear (countershaft 25).

In FIG. 3, the gear diagram of a reversing gear, having four forward andthree reverse gears, is reproduced. It is a reversing gear for shortcenter distances (approximately from 120 to 220 mm) for use in mobilecranes, lift trucks and, preferably, excavator loaders. The reversinggear can also be shown in a six-gear version. The reversing gearreproduced has functional features in common with the reversing gear ofFIG. 1 so that similar parts bear the same reference numerals. Duringthe course of the explanation that follows detailed attention will bedrawn to existing differences.

The engine 2 drives a hollow shaft 7 of the reversing gear 1 via thehydrodynamic torque converter 5. In this gear, the fixed gear 11 is alsoconnected with the hollow shaft 7. The set of driving wheels 12 isformed by the idler gears 13, 14 and 15, which are supported on thecountershafts 16, 17 and 18. The clutch 19 serves as a directionalclutch for the forward travel direction. The reverse travel direction issimilarly selected with the clutch 20.

The fixed gear 36 of the countershaft 17 meshes with a first fixed gear50 of the countershaft 16 and another fixed gear 51, of saidcountershaft 16, is in meshed connection with one fixed gear 52 of thecountershaft 23.

The fixed gears 36, 50, 51 and 52 are component parts of the set ofdistribution wheels 35. In this arrangement, the fixed gears 50 and 51are functionally similar to the fixed gears 37 and 38 of thecountershaft 18 of the reversing gear of FIG. 1. The set of distributionwheels 35 is completed by a fixed gear 53 upon the countershaft 18, thefixed gear 27 of the countershaft 24 and the idler gear 28 upon thecountershaft 25 which is, at the same time, the output shaft 22.

The chain of driven wheels 34 is formed by the fixed gear 32 of a largediameter of the countershaft or output shaft 22, the idler gear 30 ofthe countershaft 24 and the idler gear 40 of the countershaft 23.

The fixed gear 27 of the countershaft 24 is in constant mesh with afixed gear 53 which is component part of the set of distribution wheels35. Said fixed gear 53 is non-rotatably connected with the countershaft18. The fixed gears 36 and 53 are in constant mesh.

The clutches 41, 31, 29 and 21, together with the directional clutches19 and 20 are provided for gearshifting.

The individual gears are engaged as follows:

    ______________________________________                                               gear actuated clutches                                                 ______________________________________                                               1    19 and 41                                                                2    19 and 31                                                                3    19 and 29                                                                4    21 and 29                                                                1R   20 and 41                                                                2R   20 and 31                                                                3R   20 and 29                                                         ______________________________________                                    

In order that none of the idler gears are used as an intermediate gearand, in particular, in order to prevent a loosely supported intermediategear upon the countershaft or output shaft 25, 22, the countershafts 23,16, 17, 18, 24 and 25 or 22 are situated in relation to the input shaft3 or the hollow shaft 7 so as to be, so to speak, wound around theinput.

This results from the illustration according to FIG. 4 of theschematized front elevation on the gear. The position of the set ofdistributor wheels is highlighted, in particular, by a thick line 54 ofthe distribution chain. The countershafts are positioned in relation tothe input so that the power flow in said distribution chain is ledaround the input and interrupted only between the countershafts 23, 25or 22.

From the drawing, it results that the gear has a compact design withshort center distances.

The reversing gear 1, upon which is based the gear diagram of FIG. 5, isa modification both of the gear of FIG. 1 and of the one of FIG. 3. Thecoincidence with the gear of FIG. 1 exists only insofar as with saidgear a longer center distance is also to be realized.

The variation of the gear of FIGS. 1 and 3 consists in that it is to beshown, with this construction, that the gear situated upon thecountershaft 25, having a relatively large diameter, must notnecessarily be a fixed gear. It is basically possible to design thispinion as an idler gear 55 which can be non-rotatably connected by theclutch 29 with the countershaft 25. The idler gear is in constant meshedconnection with the fixed gear 33 upon the countershaft 22 of thereversing gear 1. The design of said pinion, as idler an gear 55, isdisadvantageous in itself. For the manufacturer opposed to saiddisadvantage stands the advantage of a greater freedom in the spatialarrangement of the countershafts. The diagrammatic top view of the gearof FIG. 6 shows the possible spatial arrangement of the input and hollowshafts 3, 7 situated concentrically with each other and of the remainingcountershafts. The lines which interconnect the set of distributorwheels 35, the distribution chain are, in turn, especially highlightedwith a thick line.

    ______________________________________                                        Reference numerals                                                            ______________________________________                                        1      reversing gear  30    idler gear                                       2      engine          31    clutch                                           3      input shaft     32    fixed gear                                       4      impeller        33    fixed gear                                       5      torque converter                                                                              34    chain of driven wheels                           6      turbine wheel   35    set of distribution                              7      hollow shaft          wheels                                           8      stator          36    fixed gear                                       9      converter bridge clutch                                                                       37    fixed gear                                       10     pump            38    fixed gear                                       11     fixed gear      39    fixed gear                                       12     set of drive wheels                                                                           40    idler gear                                       13     idler gear      41    clutch                                           14     idler gear      42    line                                             15     idler gear      43    line                                             16     countershaft    44    line                                             17     countershaft    45    --                                               18     countershaft    46    --                                               19     clutch          47    --                                               20     clutch          48    --                                               21     clutch          49    --                                               22     output shaft    50    fixed gear                                       23     countershaft    51    fixed gear                                       24     countershaft    52    fixed gear                                       25     countershaft    53    fixed gear                                       26     fixed gear      54    line (distribution                               27     fixed gear            chain)                                           28     idler gear      55    idler gear                                       29     clutch                                                                 ______________________________________                                    

We claim:
 1. A multi-ratio reversing powershiftable transmission (1)comprising:at least one input shaft (3, 7), having a fixed drive gear(11); a plurality of countershafts (16, 17, 18, 23, 24 and 25), eachsupporting a single clutch (19, 20, 21, 29, 31 and 41) and an idler gear(13, 14, 15, 40, 30, 28) which can be optionally non-rotatably connectedwith one of each said countershafts for a change of gear and direction;a set of drive wheels (12) consisting of said fixed drive gear (11) inconstant mesh with more than one of said idler gears; a set ofdistribution wheels (35) consisting of a plurality of fixed gears (26,27, 36, 37, 38 and 39) and one of said idler gears (28) for commutatingrotational communication between said countershafts; a set of drivenwheels (34) having at least one fixed driven gear (32) in constant meshwith at least two said idler gears (30, 40) for driving an output shaft.2. A multi-ratio reversing powershiftable transmission (1) as set forthin claim 1, wherein said one idler gear (28) of said set of distributionwheels (35) is situated upon said countershaft opposite to said onefixed gear (32) of said driven wheels (34).
 3. A multi-ratio reversingpowershiftable transmission (1) as set forth in claim 1, whereinactuating of said clutch initiates said non-rotatable connection betweensaid one idler gear (28) and respective countershaft of said set ofdistribution wheels (35) forms a third gear ratio within saidmulti-ratio reversing powershiftable transmission.
 4. A multi-ratioreversing powershiftable transmission (1) as set forth in claim 1,wherein at least one of said clutches (19, 20 or 21) respectivelyassociated with one of said idler gears of said set of drive wheels (12)is used as one of a directional and gearshift clutch.
 5. A multi-ratioreversing powershiftable transmission (1) as set forth in claim 4wherein a pair of fixed gears (37, 38) of said set of distributionwheels are supported on a countershaft corresponding with said at leastone directional and gearshift clutch (19, 20, 21), of said set of drivewheels (12).
 6. A multi-ratio reversing powershiftable transmission (1)according to claim 1, wherein at least one of said plurality ofcountershafts supports up to two fixed gears together with one saidclutch.
 7. A multi-ratio reversing powershiftable transmission (1)according to claim 1, wherein said fixed drive gear (11) of said set ofdrive wheels (12) is fixed upon said input shaft (7) which is hollow andis situated concentrically with respect to another input shaft (3).
 8. Amulti-ratio reversing powershiftable gear (1) as set forth in claim 1wherein said at least one fixed driven gear (32) is in constant meshwith a first and second idler gears having corresponding first andsecond clutches wherein activation of one of said first and secondclutches engages one of a first and second gears of said multi-ratioreversing powershiftable transmission.
 9. A multi-ratio reversingpowershiftable transmission (1) comprising:at least one input shaft (3,7), having a fixed drive gear (11); a plurality of countershafts (16,17, 18, 23, 24 and 25), each supporting a single clutch (19, 20, 21, 29,31 and 41) and an idler gear (13, 14, 15, 40, 30, 28) which can beoptionally non-rotatably connected with one of said countershafts for achange of gear and direction; a set of drive wheels (12) consisting ofsaid fixed drive gear (11) in constant mesh with more than one of saididler gears; a set of distribution wheels (35) consisting of a pluralityof fixed gears (26, 27, 36, 37, 38 and 39) and one of said idler gears(28) for commutating rotational communication between saidcountershafts; a set of driven wheels (34) having a first idler gear(55) in constant mesh with at least a second and third said idler gears(30, 40) for driving an output shaft.